I think this is only going to increase for the foreseeable future because to get the most out of each platform you have to use platform specific languages (usually). Swift for iOS, Kotlin for Android - then whatever you use on the backend and web frontend, etc. You can use things like Flutter for multiple platforms, but they’re not quite there yet for everything (though Flutter is definitely one to watch - being backed by Google).
Something I have really enjoyed about learning another language is how things are done differently, and the ideas that I can borrow and apply from one language to another.